Many people associate Hubble Space Telescope with beautiful images of the cosmos — but the truth is that the majority of Hubble's observations, while scientifically valuable, are pretty boring from a purely visual standpoint.

Yesterday, NASA announced a milestone in the almost 22-year history of its Hubble Space Telescope:…
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These "unattractive" observations so vastly outnumber the aesthetically pleasing ones, that a surprising number of Hubble's most dazzling images never see the light of day. The ESA calls these "Hubble's Hidden Treasures." Back in May, the Agency challenged the public to excavate these rare images from Hubble's prodigious science archive. Nearly 3,000 public submissions later, these are the Hubble space pictures that were selected as the very best.

Josh Lake (USA) submitted a stunning image of NGC 1763, part of the N11 star-forming region in the Large Magellanic Cloud. ESA/Hubble had previously published an image of an area just adjacent to this (heic1011), based on observations by the same team. Josh took a different approach, producing a bold two-colour image which contrasts the light from glowing hydrogen and nitrogen. The image is not in natural colours - hydrogen and nitrogen produce almost indistinguishable shades of red light that our eyes would struggle to tell apart - but Josh's processing separates them out into blue and red, dramatically highlighting the structure of the region. As well as narrowly topping the jury's vote, Josh Lake also won the public vote.

Andre van der Hoeven (Netherlands) came a close second in the jury vote. His image of the spiral galaxy Messier 77 is highly attractive, and is also an impressive piece of image processing, combining a number of datasets from separate instruments into one amazing picture. Andre entered several other noteworthy images into the competition, including a huge image of Messier 106, combining data from Hubble and other telescopes. His image of NGC 6537, a star-forming region, greatly impressed the jury too.

Judy Schmidt (USA) also entered several highly accomplished images into the competition. Her picture of XZ Tauri, a newborn star spraying out gas into its surroundings and lighting up a nearby cloud of dust, was the jury's favourite. This was a challenging dataset to process, as Hubble only captured two colours in this area. Nevertheless, the end result is an attractive image, and an unusual object that we would never have found without her help. Judy's other images also impressed our panel, in particular her images of Herbig–Haro object HH 909A and elliptical galaxy PGC 6240.

Renaud Houdinet (France) submitted a hugely ambitious mosaic of Hubble images. Chamaeleon I is a large nebula near the south celestial pole, and it does not fit into a single Hubble image. Renaud painstakingly tiled the exposures together. Despite the small gaps between the Hubble images, the jury was impressed by the technical achievement of putting together this ambitious vista.

Robert Gendler (USA) is a well known figure in the amateur image processing world. His version of Hubble's image of NGC 3190 is the default desktop image on new Apple computers. Robert submitted a number of excellent images into the competition. This image of Messier 96 was the jury's favourite.